1. The Field of the Invention
The present invention relates generally to modular orthopedic prostheses and, more specifically, to attachment mechanisms for securing components of a modular orthopedic prosthesis.
2. The Relevant Technology
Modular orthopedic prostheses offer many advantages to the user. By selecting independent modular components to construct a complete prosthesis, custom fitting of a patient's specific anatomy or specific bony condition can be accomplished.
Several attachment mechanisms are known in the art for connecting the components of a modular prosthesis. As used herein, collet refers to a thin cylindrical tube with longitudinally extending slots, such as those commonly used in the machine tool industry. For example, it is known in the art to use an interpositional, independent collet to connect one bone contacting component of a modular prosthesis to another bone contacting component of a modular prosthesis. However, the use of the independent collet adds another component to the sum of components required to construct the complete prosthesis. It would therefore be an improvement in the art to provide an attachment mechanism that would reduce the number of components required to construct a complete prosthesis in order to reduce cost and simplify the assembly technique.
Because of the high physiological loads borne by the skeletal structure, orthopedic prostheses are subject to high bending, shear, and torsional loads. However, independent collets and other fasteners all represent adjunctive components that do provide bone contacting surfaces and therefore necessarily require a reduction in thickness of the mated bone contacting components in order to accommodate the connection hardware. Thus, the mated bone contacting components are weaker due to the reduction in thickness associated with the accommodation of the connection hardware. It would therefore be an improvement in the art to provide an attachment mechanism that integrates the means of connection between modular components of a modular prosthesis into one or more of the bone contacting components.
One of the advantages of modular orthopedic prostheses is the capacity to select, at the time of surgery, a desired orientation between modular components. Many modular connections known in the art do not facilitate a state of partial assembly that closely replicates the final longitudinal configuration of the prosthesis, where, in the state of partial assembly, the modular components can be freely rotated with respect to each other. It would therefore be another improvement in the art to provide an attachment mechanism for modular prostheses that would accommodate a state of partial assembly that closely replicates the longitudinal configuration of the prosthesis while permitting free relative rotation between the modular components.